It is known to design a joint-hub unit for a driving wheel of a vehicle, wherein the joint is coupled to the hub by interposing an intermediate annular element forcefully fitted on the hub axle and axially secured to the hub by welding or cold rolling an end rim of the axle. The intermediate annular element is mounted to the joint by means of a splined coupling and is axially locked through a spring-lock ring fitted in a circular seat formed in part in the joint and in part on the intermediate annular element.
With such a unit, assembly and disassembly of the joint onto and from the hub, particularly during servicing, can result difficult, as the hub must be released from the joint by removing the spring-lock ring. A possible solution is to perform radial openings at the seat for the spring-lock ring, such as to allow to insert a tool for radially compressing the spring-lock ring and remove it from the joint. Such an arrangement, however, has the drawback of putting the inner parts of the joint in communication with the external environment.
Further, in all of the above mentioned arrangements, moisture and dirt can penetrate into the joint through the clearance of the splined coupling between the hub and the joint. Therefore, expensive and complex sealing devices must be specially provided for. These sealing devices, besides being in some instances difficult to mount, render servicing operations more difficult.